1. Field of the Invention
The present invention relates a method of, and an apparatus for producing tire carcass.
2. Description of the Related Art
Conventionally, a pneumatic tire is produced by a method in which a plurality of carcass cords are aligned and coated by rubber to form a rubber strip, which is then cut into a rubber sheet having a predetermined constant length. The rubber sheet is wound around an inner linear supported on a drum, and both ends of the rubber sheet are joined to each other. Subsequently, bead cores are fitted over the rubber sheet on both sides of the drum to form a tire carcass belt layer. The edges of the carcass belt layer are then folded about the bead cores and additional tire members, such as side rubbers and the like, are wound over the folded portions of the carcass belt layer to form a green case. The green case is then shaped into a toroidal green tire, which is then subjected to vulcanization and other steps necessary to form a product tire.
With the above-mentioned conventional tire production method, it is inevitable that a number of cut surfaces of the carcass cord are successively arranged along the folded portions of the carcass, and subjected to stress concentrations during use of the tire. Due to severe stress concentration at the cut surfaces of the carcass cord, that tends to be caused under extreme use conditions of the tire, there may occur interlayer separations at the cord ends, or other serious defects at the tire bead portions.
In view of the above-mentioned problems arising from the conventional method, JP-A-10-226,203 discloses a tire in which the bead portions are essentially free from cut surfaces of the carcass cord. In this instance, the carcass of the tire has a substantially cordless center portion which is formed by continuously applying, on each side of the tire, a carcass cord in a zigzag manner so that the cord is reciprocated between the bead core portion and that portion of the carcass belt layer which corresponds to the side edge portion of the tread rubber layer. However, except that the carcass cod is to be applied in a zigzag manner on each side of the tire, JP-A-10-226,203 does not disclose concrete measures which can be effectively used for practical production of the tire carcass.
It is highly desirable, and is thus a primary object of the present invention, to realize a practical technology for producing a tire carcass in which the bead portions are free from cut surfaces of the carcass cord. Such a technology should ensures that the carcass can be produced efficiently, without requiring noticeably complicated hardware arrangement.
According to one aspect of the present invention, there is provided an apparatus for producing a tire carcass, comprising: a substantially toroidal carrier for supporting a rubber member of a tire; an indexing mechanism for causing an indexing movement of the carrier by a predetermined angle about a rotational axis of the carrier; a feed mechanism having an outlet guide for feeding a carcass cord toward an outer surface of the carrier, said feed mechanism being reciprocable in the axial direction of the carrier within a surface region thereof, that extends axially of the carrier at least between positions of the carrier corresponding to a bead portion and a tread end portion of a tire, respectively; and pressure mechanisms forming at least a pair are arranged adjacent to opposite ends of said surface region of the carrier, respectively, so that the carcass cord fed from the feed mechanism is wound about the respective pressure mechanisms and urged thereby toward the outer surface of the carrier.
The pressure mechanisms may be arranged adjacent to those positions of the carrier, which correspond to opposite bead portions of a tire, respectively. Additionally, or alternatively, the pressure mechanisms may be arranged adjacent to those positions of the carrier, which correspond to the bead portion and the tread end of the tire, respectively.
The apparatus according to the present invention may comprise two pairs of the pressure mechanisms arranged adjacent to those portions of the carrier, which correspond to opposite bead portions and opposite tread ends of the tire, respectively.
Preferably, the pressure mechanisms each comprise a pin about which the carcass cord can be would, drive means for moving the pin into, and out of contact with the outer surface of the rubber member on the carrier, and a pressure member for urging the carcass cord, which has been wound about the pin, toward the outer surface of the rubber member on the carrier.
The apparatus according to the present invention may further comprise at least one deflection mechanism arranged between the pressure mechanisms forming a pair, for changing the direction in which the carcass cord extends along the outer surface region of the carrier.
The feed mechanism may comprise a three-axes actuator that is adapted to move the carcass cord along the outer surface of the carrier.
According to another aspect of the present invention, there is provided a method of producing a tire carcass, comprising the steps of: supporting a rubber member on a substantially toroidal carrier; operating an indexing mechanism and thereby causing an indexing movement of the carrier by a predetermined angle about a rotational axis of the carrier; operating a feed mechanism synchronously with the indexing mechanism, so that said feed mechanism is reciprocated in the axial direction of the carrier within a surface region thereof, that extends axially of the carrier at least between positions of the carrier corresponding to a bead portion and a tread end portion of a tire, respectively, and a carcass cord is fed through an outlet guide in the feed mechanism toward an outer surface of the carrier; and operating at least a pair of pressure mechanisms synchronously with the indexing mechanism, said pressure mechanisms being arranged adjacent to opposite ends of said surface region of the carrier, respectively, so that the carcass cord fed from the feed mechanism is wound about the respective pressure mechanisms and urged thereby toward the outer surface of the carrier.
In the method according to the present invention, at least one deflection mechanism may be provided between the pressure mechanisms. In this instance, the carcass cord is engaged with the deflecting mechanism so as to change the direction of the carcass cord along the outer surface region between said pressure mechanisms and thereby form a carcass in which the carcass cord has a deflected center region.
In the method according to the present invention, furthermore, the feed mechanism and the pair of pressure mechanisms may be provided for each side of the tire. In this instance, the feed mechanism and the pressure mechanisms on one side of the tire are operated simultaneously with the corresponding feed mechanism and the corresponding pressure mechanisms on the other side of the tire, respectively.